Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity.
In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart which is of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical and largely determines how useful the catheter is.
Steerable (or deflectable) catheters are generally well-known. For example, U.S. Pat. No. RE 34,502 describes a catheter having a control handle comprising a housing having a piston chamber at its distal end. A piston is mounted in the piston chamber and is afforded lengthwise movement. The proximal end of the catheter body is attached to the piston. A puller wire is attached to the housing and extends through the piston and through the catheter body. The distal end of the puller wire is anchored in the tip section of the catheter. In this arrangement, lengthwise movement of the piston relative to the housing results in deflection of the catheter tip section.
Often it is desirable to have a bidirectional steerable catheter, i.e., a catheter that can be deflected in two directions, typically opposing directions. For example, U.S. Pat. No. 6,210,407 discloses a bidirectional steerable catheter having two puller wires extending through the catheter. The distal ends of the puller wires are anchored to opposite sides of the tip section of the catheter. A suitable bidirectional control handle is provided that permits longitudinal movement of each puller wire to thereby allow deflection of the catheter in two opposing directions.
Also known is a steerable catheter having a tip section deflection mechanism is disclosed in U.S. application Ser. No. 11/058,102, filed Feb. 14, 2005, entitled STEERABLE CATHETER WITH IN-PLANE DEFLECTION, the entire disclosure of which is hereby incorporated by reference. However, the deflection mechanism can be improved upon for reinforced tubing, including braided tubing made by the Maypole or sinuous method.
Catheter shafts typically comprise an elongated tubular construction having a single, axial or central lumen. They are flexible, i.e., bendable, but substantially non-compressible along their length. Catheter shafts often have an outer wall made of polyurethane or PEBAX that has an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the catheter shaft so that rotation at one end (for example, by rotation of a control handle), the shaft will rotate in a corresponding manner through to the other end.
The braided mesh is typically constructed from at least two strands which are wound in oppositely directed helical paths that pass over and under one another in a prescribed sequential interval such as by a maypole or sinuous braiding machine. Maypole-type braiders for the reinforcing of hose and other tubular products and for the production of ropes, cables and the like are known and patented. Patents include U.S. Pat. Nos. 3,371,573, 3,783,736 and 5,257,571, the entire disclosures of which are hereby incorporated by reference. More modern braiding machines have a mechanism for directing strand supply carrier spindles in intersecting serpentine paths around a braiding point. The mechanism includes a circle of carrier spindle drivers, where each carrier spindle has independent rotation from the driver it is driven thereby so that there is no abrupt change of direction of rotation as it is transferred from a rotor rotating in one direction to a rotor rotating in the opposite direction. Moreover, the braider is also configured so that a strand pay-off point of each carrier is maintained substantially on a line drawn through the center of the spindle and the braiding point during the travel of the carrier spindles in their serpentine paths around the braiding point. Suitable braiding machines for manufacturing reinforced tubing are available from Steeger USA, Inman, S.C., USA.
Although braided and reinforced tubing, and catheter shafts constructed therefrom have better torsional characteristics which minimize kinking and twisting of the shafts, there is need for a tubing construction that integrates the various layers and reinforcement components with a biasing mechanism to promote in-plane deflection, that is, where deflection of at least a portion of the shaft is in the same plane in which the pair of puller wires span. Such a catheter would have greater resistance to out-of-plane deflections to provide more predicable and precise steering of the catheter tip. Accordingly, a need exists for a catheter having an integrated tubing construction that is biased for in-plane bi-directional deflection.